In order to realize the SCRAM jet engine which is the most promising propulsion system for space planes and hypersonic transports, this research project aims at fundamental study in the four important fields :(1) Air intake, (2) Fuel injection and mixing, (3) Supersonic combustion, and (4) Thermal protection structure and materials.(1) In the air intake research the focus was put on the stable operation of inlets, and compound choking phenomena due to sucking of airframe boundary layer flows into engine and transient unstart and restart phenomena were investigated. Results show that the airframe boundary layer flow easily leads engines unstart, but that the swept side cowl inlet easily recovers from unstart to restart.(2) The study on fuel injection and mixing progressed understandings on flow mechanics and turbulent mixing process of fuels injected into a supersonic stream. Two-dimensional as well as three-dimensioanl injection experiments were conducted, and the correlation between mixing efficiency and total pressure loss were clarified. Numerical simulation technique for a two-dimensional injection model was established.(3) The purpose of supersonic combustion is first to realize combustion of hydrogen in the supersonic stream, and secondly to study importance of factors which control supersonic combustion processes. In the experiments parallel-to-flow injection as well as normal-to-flow injection were adopted, and the effect of combustion on flow mechanics were made clear via optical observation on the structure of shock waves and flames.(4) In the field of thermal protection structure and materials, a high performance cooling structure was constructed applying the heat pipe concept to a two-dimensional panel, and its basic characteristics were studied. In the research for high temperature materials, the fracture mechanics of ceramics were investigated especially on the relation between the strength of grain boundaries and temperature.